Who Creates Assembly Drawings?

[fogleghorn]

Our company produces analytical instruments. Each instrument typically has a cabinet made out of painted sheetmetal, a printed circuit board card cage assembly with a mother board, a power supply assembly, and some type of analysis module assembly. 3D models of these sub-assemblies as well as the final assembly are created in our CAD package. Step-by-step exploded assembly drawings are created for each of the sub-assemblies as well as the final assembly by the mechanical engineers; sometimes with the help of a draftsman. Creating these drawings can be quite time consuming. There is a push from the Director of Engineering to get the manufacturing engineers to work with the draftsman to get the assembly drawings created in order to free up the mechanical engineers to work on new designs. I was wondering if anyone else out there had tried this scenario; and I am particularly interested in what worked well and what didn't.

 

[MadMango]

I have worked places where engineers only gave data and napkin sketches to drafters to create finished drawings for review, which was an extreme.

I have also seen where engineers will do basic layout models and data and let drafters finish-detail the models and create all associated documents for review, which seems more common.

I have heard of places where the engineers have to do everything with the models and documents, which is the other extreme.

Depending on your CAD software, creation of assembly drawings can be easy or tedious, more info is required.

"Art without engineering is dreaming; Engineering without art is calculating."

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[drawoh]

fogleghorn,

I create assembly drawings as part of my design process. This allows me to analyze the assembly procedure.

Assembly must be possible.

In production, assembly must be efficient. At the design stage, I sometimes work out assembly and test fixtures. This often feeds back to my design.

I want to implement good DFMA procedures. At the design level, if I generate assemblies and parts lists, I can standardize fasteners and other hardware. Manufacturing is not in control of clearance holes and flange thicknesses.

Sub-assemblies should be modular. This stuff all is fixed at the design level. Once you do not make it modular, there is nothing production can do.

Once, on a complicated module, I created an arrangement drawing. I copied this over to start off the assembly drawing. As I worked up the assembly drawing, I wrote separate assembly instructions. I made a lot of design modifications as I did this, to make those instructions work.

If you are designing a highly standardized product, you should be able to automate your design and documentation process. In SolidWorks, it is often possible to set up a set of template files which you hack to customer requirements. Assembly drawings would be part of the template, and would require little more than tweaking on a project by project basis.

JHG

 

[ctopher]

It is very common for engineers to create the 3D models (if they know how), send to designers/drafters to have drawings created.
I worked for a few companies that have worked this way. It frees up the engineers for other work.
Usually engineers don't have the time or the know-how to create the drawings.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

 

[fogleghorn]

We are using Solid Edge, and we also design with modular/testable sub-assemblies. Our assembly drawings can have up to 100 separate line items on the Bill of Materials. Our step-by-step assembly drawings can require up to 20 B-size or C-size sheets.

Our manufacturing engineering department says that since we (the mechanical engineers) designed the instrument, we are the ones that know how it should go together, and therefore we are best suited for creating the assembly drawings. I have found that in the amount of time that it takes for me to explain how each exploded view should look, I can create the view myself and place that view on one of the sheets of the assembly drawing. Still, our Director of Engineering (D of E) wants to off-load this task onto the manufacturing engineers and draftsmen. I might add that our (D of E) is a software engineer by trade.

 

[KENAT]

fogleghorn, it almost sounds like you work at the same place as me.

Historically we had a mess, a lot of hybrid assembly drawings/assembly work instructions see thread1103-157857. Many created by Engineering some by Manufacturing. We also had product lines with nothing more than a Bill of Materials and maybe a binder somewhere with a few hand written notes & a couple of photographs!

While we are still implementing it, we have now drawn a distinction between Assembly Drawings & Assembly work instructions.

An ASME Y14.24 compliant Assembly drawing is fairly quick to produce, at least with the CAD packages I'm familiar with. It does not have assembly instructions (which would contravene ASME Y14.5M-1994) but does show the part (and all components) in it's assembled state using sections etc as required, gives a parts list, identifies all parts and states any additional explicit requirements. Essentially if fully defines the intended finished article.

There is then as separate assembly work instruction which gives details on how to best assemble the item. This is less formal and uses step by step exploded views & ‘partial’ views only showing select components from the CAD as well as things like photographs. It gives information on what tools to use etc. It sometimes also helps define things that can be difficult/time consuming to fully detail on a drawing, such as cable & tubing routings etc. We’ve even looked at software that can create a ‘step by step’ web page using 3D model/viewer to do this. These are very time consuming to make, and because we ‘validate’ them with the shop floor on several builds can take a long time to get finalized.

(My – not that I have much say) Eventual plan is that 'Engineering' (mostly engineers with a couple of drafters/designers and some interns that mainly do drafting work) will prepare the assembly drawings to define the assembly.

Manufacturing ‘Engineers’ and their interns will prepare the work instructions.

At present, it’s still a mess as regards who does what. We have Design/Engineering creating work instructions while Manufacturing are correcting drawings and other traditionally ‘Engineering’ tasks.

At previous employers it was definitely Manufacturing/Productions job to create work instructions be it a formal document, notes on the routing/traveler, placards at work stations or whatever. Design/Engineering had little to do with this, just producing conventional assembly drawings. We had design reviews to get manufacturing’s input and did keep DFMA etc. in mind, but we didn’t actually do work instructions.

Essentially Design/Engineering determined what had to be manufactured, Manufacturing Engineering determined how best to achieve this.


KENAT, probably the least qualified checker you'll ever meet...

 

[KENAT]

fogleghorn, we use Solid Edge too. Are you sure we aren't in the same office!

Beware, while explosions in Solid Edge are quick to produce - they are not very robust. If you later swap/change parts in the assembly the explosions often fail. If you have a bunch of notes etc. attatched to the explosion, and depending how you've done it etc this can be a nightmare.

KENAT, probably the least qualified checker you'll ever meet...

 

[fogleghorn]

KENAT, doesn't sound like the same company, but it's pretty close. Our Manufacturing Engineering Department doesn't create any drawings, they want everything on the exploded assembly drawings that are currently produced by mechanical engineering.

"These are very time consuming to make, and because we 'validate' them with the shop floor on several builds can take a long time to get finalized."

This is exactly what we do, and I agree that it can take a long time to get the exploded assembly drawings finalized.

 

[KENAT]

From a selfish PLC/project release point of view...

As conventional drawings are faster to produce it can significantly reduce development timescales.

Product can be released for manufacture based on the drawings. (Freeing Engineering to get on with the next product.)

During initial production assembly processes can be fine tuned by manufacturing and documented however they see fit, be it CAD generated exploded view assembly instructions or placards at work stations etc.

We are in an industry where 'time to market' is critical. If I could persuade them of the above I think it would help.

KENAT, probably the least qualified checker you'll ever meet...

 

[aardvarkdw]

Fogleghorn,

At my last company we had a situation where the design/mechanical engineers were so busy with the "next big thing", that they would produce part models, take a stab at detailing them (more often then not, incorrectly), and generate an assembly model that usually did not include fasteners, cables, and the myriad of incidental components required to build the device (glue, washers, gaskets, etc...). They would then drop the mess on the manufacturing engineer's desks and they would be left on their own to figure out how to build the product from the bits. This usually involved having a designer come down and help the ME's build a machine from which they would produce the assembly drawings/manufacturing instructions. Then when the first 5 or so were built, they would fail and the engineers would ask why "insert component here" wasn't installed properly or "insert process here" wasn't followed.

I guess what I am getting at is that the designer knows what was intended a lot better than the ME does. Before I left I made marginal headway into implementing a process that would require the designers to produce an assembly drawing (all components listed and identified, critical dimensions shown and all other information necessary to describe the product) and the ME's would then use this to create their assembly documentation.

The designers should not waste their time telling the assemblers how best to build the product, that is the ME's job. They do however have critical information that needs to be given to the ME's first, and it is best and quickest communicated in an assembly drawing.

David

 

[ewh]

My experiences agree with the others... usually Design Engineering defines the assembly, Manufacturing Engineering defines the assembly procedures.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - [small]Thomas Jefferson [/small]

 

[fcsuper]

Sometimes we use detailed work instructions only, and sometimes we use assy dwgs with basic work instructions.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[drawoh]

ewh,

Ultimately, the assembly procedure is controlled by the design. Manufacturing can fix details. It is like those cars where you have to winch the engine out of the car to change the spark plugs. Drafters and technical writers have to document stuff like this. As the designer, you fix the problem. A software designer once told me that the first step to developing software is to write the manual.

In my copy of Design for Manufacture and Assembly (Boothroyd, Dewhurst and Knight), it is claimed that 70% of manufacturing costs are locked in by the designers. If manufacturing is going to be a significant or dominant part of total cost, the designers must review the assembly procedure and verify that at least something will work.

At some point, you look at your assembly procedure and you realize that it sucks, and that you can fix the design so that it does not suck.

JHG

 

[fogleghorn]

Thanks for all the input on this topic, and KENAT, thanks for the link to your previous thread dealing with the same subject matter. As I suspected, different companies are doing different things. Although, it does seem that most entries on this thread and on KENAT's previous thread favor an assembly drawing from Engineering that doesn't give specific step-by-step build instructions, and that those specific step-by-step build instructions are the responsibilty of the Manufacturing Engineering Departmet.

 

[MadMango]

That's a good summary.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[ewh]

Ultimately, the assembly procedure is controlled by the design

Yes, in the sense that it must be assembled to meet the assembly drawing. In a stricter sense, no. The drawing defines only what the final result is to be. Achieving that result is ultimately a Manufacturing Engineering role. Directing assembly steps on an assembly drawing is akin to directing machining steps on a detail drawing. Unless it is necessary for the function of the part, any steps to achieve the desired result are left to the descretion of the fabricator.
I fully support DFMA, but this we're not talking software. It has been a design role for as long as I have been a designer to take this into consideration; it has not, however, been my responsibility to define what steps are to be taken to make the part, be it an assembly or a machined part, unless, as I have noted, it is critical to the function of the part.
Yes, someone has to review and document how something is made, but again, that is more a Manufacturing Engineering group role than a design group role. If there are assembly or fabrication problems that have been overlooked by the designer, the manufacturing group can communicate/i] that back to the design group, and the design can be revisited to address those specific concerns.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - [small]Thomas Jefferson [/small]

 

[ewh]

I didn't intend to sound so rigid in my previous post.
Just because someone is in the Design Engineering group does not mean that they can not take on a Manufacturing role. I have often completed inspection drawings and assembly sequence illustrations for other groups, but only at their request, or because that role was not filled by someone else. Many companies can not afford to strictly limit who does what role, but the roles are still different.
So I guess the gist of my comments is that I disagree with ths statement that "Ultimately, the assembly procedure is controlled by the design". IMO, ultimately, the assembly proceedure is controlled by manufacturing, based on the design.

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - [small]Thomas Jefferson [/small]

 

[drawoh]

ewh,

The ideal case is that manufacturing selects the most efficient procedure from an infinite range of possible methods. The worst case is that no assembly methods work, or only one assembly method works, and it is not very good. This is all a function of design.

If the part is to be manufactured in any sort of quantity, the designers should demonstrate an efficient assembly procedure at the final design review. If manufacturing finds a more efficient way, that is nice.

I have generated assembly drawings that clearly showed the assembly sequence. I did this because I knew that things had to be done in order if they were going to go together. If sequence or other specific procedures do not matter, I do not document them.

JHG

 

[ewh]

I guess we'll have to agree to disagree. I feel that communication and teamwork should ensure that something can be efficiently assembled, but it is still ultimately a manufacturing responsibility, regardless of who actually does the work.
All of the approval blocks on drawings and change orders that I am familiar with have a space for manufacturing to sign off, certifying that they have reviewed and accepted the design. If not for manufacturability, then what?

When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - [small]Thomas Jefferson [/small]

 

[MadMango]

Phase Gates (or whatever they are called today) help with that communication and teamwork, and while manufacturing holds the responsibility, design can surely make their jobs easier the sooner both get involved.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?